• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.274-277
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• 2008

Rekeying is the process of changing the encryption key of an ongoing communication. The main objective is to limit the amount of data encrypted with the same key. The IEEE 802.11 standard defines the Wired Equivalent Privacy, or WEP, encapsulation of 802.11 data frames. MAC at sender encrypts the payload (frame body and CRC) of each 802.11 frame before transmission using RC4 stream cipher. MAC at receiver decrypts and passes data to higher level protocol. WEP uses symmetric key stream cipher (RC4) where same key will be used for data encryption and decryption at the sender and the receiver. WEP is not promising with the advancement of the wireless technology existing today. We propose to use the existing information to define the security attributes. This will eliminate the steps that regenerated keys have to be sent to each other over certain period. The rekeying scheme is according to the number of bytes transmitted. Therefore, even the attacker has recorded the packets, it will be insufficient information and time for the attacker to launch the attacks as the key is not deterministic. We develop a packet simulation software for packet transmission and simulate our propose scheme. From the simulation, our propose scheme will overcome the weak WEP key attack and provide an alternative solution to wireless packet transmission. Besides that, our solution appears to be a software approach where only driver updates are needed for the wireless client and server.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1597-1605
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• 2015

Password authenticated key exchange (PAKE) is a protocol that a client stores its password to a server, authenticates itself using its password and shares a session key with the server. In multi-server PAKE, a client splits its password and stores them to several servers separately. Unless all the servers are compromised, client's password will not be disclosed in the multi-server setting. In attribute-based encryption (ABE), a sender encrypts a message M using a set of attributes and then a receiver decrypts it using the same set of attributes. In this paper, we introduce multi-server PAKE protocol that utilizes a set of attributes of ABE as a client's password. In the protocol, the client and servers do not need to create additional public/private key pairs because the password is used as a set of public keys. Also, the client and the servers exchange only one round-trip message per server. The protocol is secure against dictionary attacks. We prove our system is secure in a proposed threat model. Finally we show feasibility through evaluating the execution time of the protocol.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.257-260
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• 2002

This paper describes a design of cryptographic processor that implements the AES (Advanced Encryption Standard) block cipher algorithm“Rijndael”. To achieve high throughput rate, a sub-pipeline stage is inserted into the round transformation block, resulting that the second half of current round function and the first half of next round function are being simultaneously operated. For area-efficient and low-power implementation the round transformation block is designed to share the hardware resources in encryption and decryption. An efficient scheme for on-the-fly key scheduling, which supports the three master-key lengths of 128-b/192-b/256-b, is devised to generate round keys in the first sub-pipeline stage of each round processing. The cryptoprocessor designed in Verilog-HDL was verified using Xilinx FPGA board and test system. The core synthesized using 0.35-${\mu}{\textrm}{m}$ CMOS cell library consists of about 25,000 gates. Simulation results show that it has a throughput of about 520-Mbits/sec with 220-MHz clock frequency at 2.5-V supply.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.11
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• pp.33-43
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• 2002

This paper describes a design of cryptographic processor that implements the AES (Advanced Encryption Standard) block cipher algorithm "Rijndael". To achieve high throughput rate, a sub-pipeline stage is inserted into a round transformation block, resulting that two consecutive round functions are simultaneously operated. For area-efficient and low-power implementation, the round transformation block is designed to share the hardware resources for encryption and decryption. An efficient on-the-fly key scheduler is devised to supports the three master-key lengths of 128-b/192-b/256-b, and it generates round keys in the first sub-pipeline stage of each round processing. The Verilog-HDL model of the cryptoprocessor was verified using Xilinx FPGA board and test system. The core synthesized using 0.35-${\mu}m$ CMOS cell library consists of about 25,000 gates. Simulation results show that it has a throughput of about 520-Mbits/sec with 220-MHz clock frequency at 2.5-V supply.

• Journal of KIISE
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• v.42 no.9
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• pp.1100-1108
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• 2015

Classes.dex, which is the executable file for android operation system, has Java bite code format, so that anyone can analyze and modify its source codes by using reverse engineering. Due to this characteristic, many android applications using classes.dex as executable file have been illegally copied and distributed, causing damage to the developers and software industry. To tackle such ill-intended behavior, this paper proposes a technique to encrypt classes.dex file using an AES(Advanced Encryption Standard) encryption algorithm and decrypts the applications encrypted in such a manner in order to prevent reverse engineering of the applications. To reinforce the file against reverse engineering attack, hash values that are obtained from substituting a hash equation through the combination of salt values, are used for the keys for encrypting and decrypting classes.dex. The experiments demonstrated that the proposed technique is effective in preventing the illegal duplication of classes.dex-based android applications and reverse engineering attack. As a result, the proposed technique can protect the source of an application and also prevent the spreading of malicious codes due to repackaging attack.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.3
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• pp.34-38
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• 1984

The master key on the multiuser MH public key cryptosystem, can be substituted for multiple private keys, is proposed and derived. Applying it to public key cryptosystem, it can be possible to save memory size by selecting the master key and easy to authenticate the truth of message and the identity of the sender. Vsing this master key, it is proved that the encryption time ratio of MH method is smaller than that of RSA's method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.5
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• pp.2346-2352
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• 2011

E-mail systems using the intranet is widely exposed to internal threats should an administrator or a third party decides to misuse the information. To solve this problem, we propose a safe intranet email encryption protocol using the symmetrical-key password algorithm. Since the proposed protocol encrypts the data using a pre-agreed session keys between the users, the data will be safe from malignant access attempts provided that the session key is not exposed.

• The Journal of Information Technology
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• v.1 no.2
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• pp.229-244
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• 1998

In this paper, we discussed various securities of electronic signature. Merchants or sellers must address all Internet security concerns. Security technology may secure the routes of Internet communication, but it does not protect consumers from people with whom they might choose to do business. To Protect consumer information, they must maintain physical security of their servers and control access to software passwords and private keys. Techniqaues such as secret and public-key encryption and digital signatures play a crucial role in developing consumer confidence in electronic commerce.

• Journal of Korea Multimedia Society
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• v.23 no.5
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• pp.658-666
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• 2020

PGP is an encryption software designed to provide information protection, security and authentication services for online communication systems. The characteristic of behavior done on the Internet is that you don't know the other person. It is very important to protect information from someone you cannot trust. So identification of the other person is an important task. PGP uses an digital signature algorithm to verify the identity of the other party. However, it is not accurate to check the other party's credibility. PGP increases trust as other users sign more on public keys of user. In other words, credibility is not perfect. In this paper, PGP certification system that key management in Ethereum blockchain, one of the blockchain platforms, is proposed. Key management in blockchain ensures data integrity, transparency and reliability.

• The Transactions of the Korea Information Processing Society
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• v.7 no.6
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• pp.1903-1910
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• 2000

The objective of this paper was to cope with the verification of the message transfer protocol that integrates the electronic signature and the distribution and authentication of public key in TCP/IP using fuzzy integral. They were classified into the security technology, the security policy, the electronic document processing, the electronic document transportation and the encryption and decryption keys in its function. The measures of items of the message security protocol were produced for the verification of the implemented document in every function.